A Nelson teenager has been jailed for repeatedly stabbing a man in an argument over a sausage roll.

Two of Darryl Lee Greenwood's friends stole the sausage roll from a man at a central Nelson petrol station and taunted him with it, before getting into a fight with the man's girlfriend, during a night out on October 14 last year.

While the victim and his girlfriend walked away, Greenwood and his friends would not let the matter drop, following them and getting into a fight, during which Greenwood stabbed the man.

The details emerged as Greenwood was sentenced in the Blenheim District Court yesterday.

Judge Denys Barry sentenced Greenwood, 19, to two years and two months in prison after he admitted a charge of assault with intent to cause grievous bodily harm.

Greenwood also received his first strike under the three strikes law.

Judge Barry said Greenwood punched the victim around the head, and the two began to fight before Greenwood pulled the knife and stabbed the man in the shoulder and stomach.

"It was only when it embedded in his stomach he realised he had been stabbed, and tried to get [the knife] away from you."

As the pair struggled, the victim was also cut on the arms, chest, head and back, before managing to pin Greenwood to the ground, Judge Barry said.

The victim spent four days in hospital.

Greenwood had no previous criminal convictions or history of violence, and his actions had shocked people who knew him and himself, Judge Barry said.

A pre-sentence report showed Greenwood had been using alcohol and cannabis heavily, and was more drunk than he had ever been on that night.

Defence lawyer Mark Dollimore said Greenwood did not think that being drunk was an excuse for his behaviour.

Greenwood handed himself in to police the day after the stabbing and immediately accepted responsibility, Dollimore said.

He had cried while looking at pictures of the man in hospital, and had offered to pay the man reparation as soon as he was able to.

Greenwood had been doing well before moving out of his foster parents' home and beginning to associate with his older brother and his friends, who were a bad influence on him, Dollimore said.

He was motivated to address his problems, had started some courses, and had taken on two cleaning jobs during his two months in custody awaiting sentencing.